Demands for higher data rates for mobile services are steadily increasing. At the same time modern mobile communication systems, such as 3rd Generation systems (3G) and 4th Generation systems (4G), provide enhanced technologies, which enable higher spectral efficiencies and allow for higher data rates and cell capacities. One of the mobile communication systems currently under standardization by the 3rd Generation Partnership Project (3GPP) is the Long Term Evolution (LTE) system, the LTE-Advanced (LTE-A) system, respectively.
In LTE, each data transmission is usually signaled to a mobile transceiver or User Equipment (UE) via a control channel known as the Physical Downlink Control CHannel (PDCCH). Since the UE is not aware in advance of the exact format of the PDCCH, nor the exact transmission resources used for it, it has to perform multiple blind decodings of different possibilities in each sub-frame to check for the presence of a PDCCH addressing said UE. The information provided using the PDCCH is also called Downlink Control Information (DCI) , and it may correspond to system information, random access control, paging and group power control commands. DCI formats may comprise a format for transmission of an UpLink Shared CHannel (UL-SCH) allocation, a transmission of a DownLink Shared CHannel (DL-SCH) allocation for Single Input Multiple Output (SIMO) operation, for a compact transmission of DL-SCH allocation for SIMO operation or allocating a dedicated preample signature to a UE for random access, a transmission control information of Multiple Input Multiple Output (MIMO) rank 1 based compact resource assignment, a very compact transmission of a Physical Downlink Shared Channel (PDSCH) assignment, a transmission with additional information of power offset, a transmission of DL-SCH allocation for closed and open loop MIMO operation, a transmission of a Transmit Power Control (TPC) command for an uplink channel, etc.
In Release 8 (Rel-8) of LTE, a UE monitoring the PDCCH needs to do 44 blind decoding attempts per sub-frame, which are arranged in two sets of transmission resources or coding combinations known as “search spaces”, one is referred to as the Common Search Space (CSS), as it is shared between multiple UEs, and the other is referred to as UE Specific search Space (UESS). The number of blind decodes in the CSS in Release 8 is 12, while in the UESS it equals 32.